Friday, October 17, 2014

Previewish, Part 1: Defense

I had grand delusions about making several off-season posts, but then I realized that hanging out with my toddler was more fun. With Northwestern hosting McKendree for a basketball exhibition in four weeks, though, I have decided to jump right into the 2014-15 season. Herewith are some thoughts on what we might see from the Wildcat defense this season.

The most encouraging thing about the 2013-14 season was the ‘Cats’ defense. The team finished with an Adjusted Defensive Rating of 94.2, good enough for 14th in country. The only other time NU was in the top 25 in the KenPom era was 2001-02 (92.5, 21st). Within in the conference, NU was 5th in defensive efficiency (103.0, slightly better than the average of 103.8), not bad considering the B1G was once again the best overall conference in the nation.

My favorite thing about NU’s defense was the fact that the coaches showed a great deal of schematic flexibility. I saw straight man-to-man, 2-3 zone, 1-3-1 zone, and ultimately a switching no-middles man/zone hybrid. The graph below shows how NU was pretty good most of the non-conference slate. The game-by-game defensive efficiency tracked pretty closely to the quality of the opponent and was better than D1 average in 9 of 13 games. It also shows how the first three B1G opponents torched the ‘Cats. It was after those games that NU started switching everything on the perimeter with JerShon Cobb handling more PG minutes, and the results were (for the most part) much better.

So, if you’re looking for a reason to be optimistic about 2014-15, you can start with the defense. I don’t expect Coach Collins to ease off on emphasizing defensive intensity, and Sanjay Lumpkin and JerShon Cobb have both proven to be good defenders in the B1G. It’s not unreasonable to think Alex Olah could grow into an above-average post defender in his third season. What’s more, there is a strong correlation between defensive efficiency from one season to the next, as you can see in the chart below.*

Let’s break the defense down into some smaller components: Dean Oliver’s four factors and what Ken Pomeroy calls miscellaneous & style components.

Here we see that the primary driver of NU’s excellent defense was its opponents’ poor shooting (eFG%). The ‘Cats were below average at forcing turnovers and slightly above average in corralling defensive rebounds and not sending opponents to the foul line. We can break the poor shooting down even further to see that NU’s opponents shot poorly everywhere: from 3P, from 2P, and from the foul line. That’s great.

There is a noticeable, though not overwhelming, correlation between defensive eFG% numbers from one season to the next. 

More pronounced is the correlation between defensive 2P% numbers from one season to the next. The good news there is that NU was great at defending 2P shots last year, and it’s reasonable to think it can be again this year.

Where NU is likely to regress is in defensive 3P% and FT%. Ken Pomeroy has done extensive work examining the effect of a defense on opponents’ 3P% and found it to be minimal at best. In other words, teams that post great defensive 3P% one year are just as likely to post bad defensive 3P% the next year. There is more luck than skill to defensive 3P%.

The same holds true for defensive FT%, which is driven even more by sheer luck than anything else. This means that NU is likely to give up more points behind the arc and at the line this year than it did last year.

However, NU was pretty good at not letting opponents shoot 3P shots and not sending opponents to the foul line. Defensive strategy greatly impacts the number of 3PAs an opponent gets, and as such there is a good correlation between 3PRate from one season to the next. Free throw rate seems to be more variable. In other words, expect NU to be stingy in giving up 3PAs again this year, but be prepared to watch NU send opponents to the line more frequently. Or not; the 'Cats could again be very good at not fouling much.

If NU does surrender more points behind the arc and at the foul line, then there are other areas where it can improve: rebounding and turnovers. Chris Collins has already mentioned that generating turnovers will be more emphasized, so I'm excited about that. The biggest potential downside for this year's defense is the fact that NU will likely be reliant on two or three freshman for major minutes. I imagine the coaches will be just as willing to make in-seasons adjustments this year as they were last year, and I expect NU to again be a good national and an average (or better) B1G defensive team.

Now, the offense...well, that's next week's post.

*Data for year-to-year charts encompasses all D1 teams from 2001-2014.

And here's a song I like: Teenage Fanclub covering Alex Chilton's "Free Again"